1. Field of the Invention
The present invention relates to an information recording medium/information storage medium (or data structure), an information recording/playback method, and an information recording/playback apparatus, which are suited to record/play back a digital stream signal (MPEG-TS) used in satellite digital TV broadcast or terrestrial digital TV broadcast.
2. Description of the Related Art
In recent years, TV broadcast has entered the era of digital broadcasts having Hi-Vision programs as principal broadcast contents. The current digital broadcast adopts an MPEG transport stream (to be abbreviated as MPEG-TS as needed hereinafter). In the field of digital broadcast using moving pictures, MPEG-TS will be used as a standard format in the future.
At the start of such digital TV broadcast, market needs for a streamer that can directly record digital TV broadcast contents (without digital/analog conversion) are increasing. As a currently, commercially available, typical streamer that directly records digital broadcast data (MPEG-TS or the like), a video cassette recorder (D-VHS streamer) named D-VHS® is known.
Upon stream-recording digital broadcast data, MPEG-TS data of digital broadcast received by a tuner system (normally, a set-top box called an STB) is input to a D-VHS streamer via an IEEE1394 cable. The streamer executes required encoding processes, and records the encoded data on a D-VHS tape. Note that IEEE1394 is the interface standard, which specifies exchange of commands and transmission/reception of data.
Upon playing back broadcast data, the D-VHS streamer reads recorded data (MPEG-TS data or the like) from the recorded D-VHS tape, and sends the read MPEG-TS data to a data expansion unit in the STB via the IEEE1394 cable. In this way, the recorded data is played back.
Since the D-VHS streamer directly records the broadcasted bitstream on a tape, a plurality of programs are multiplexed and recorded on the tape. For this reason, upon playback of the multiplexed recorded programs, the D-VHS streamer sends all data to the STB regardless of whether they are to be played back from the beginning or middle of a program. In this case, the user selects and plays back a desired one of a plurality of multiplexed recorded programs.
Since a tape is used as a recording medium, the D-VHS streamer can make sequential playback but cannot make a random access to the recorded contents. For this reason, it is difficult to quickly jump to a desired position in the desired recorded program and to start playback from that position (difficulty of special playback).
In addition to D-VHS, in recent years, STBs that use hard disc drives (HDD) are put on the marker as a digital broadcast streamer. This STB saves stream data in an HDD and realizes excellent random access performance. However, in this apparatus, the user cannot easily exchange the HDD. For this reason, such apparatus is not suited to preserve a large volume of recorded data as a library over a long term.
As a prevailing solution to the problems (difficulty of random access/difficulty of special playback) of D-VHS, and that (difficulty of media exchange) of the HDD, a currently, commercially available streamer that uses large-capacity disc media such as a DVD-RAM and the like may be used.
As an example of the “streamer using the DVD-RAM”, “Digital Video Recording System” disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-268537 (patent reference 1) is known.
“Digital Video Recording System” disclosed in patent reference 1 is premised on a specific streamer standard. As an example of this streamer standard, the DVD stream recording standard (Version 1.0) developed February of 2001 (although it is not open to the public) is known (but, no product using this standard is yet commercially available).
This streamer standard aims at scrambled contents and also broadcast contents of various worldwide broadcast stations. For this reason, a minimum playback unit in video contents is defined by a data amount with reference to ECC blocks. For this reason, upon making special playback, even when data is read out from a target address, I-picture data that can be played back is not found, and the playback start position may shift considerably. That is, it is very difficult for this standard to attain special playback.
The streamer standard has contents unsuitable for special playback. However, in patent reference 1 above, special playback is facilitated by matching the head of a data unit (VOBU/SOBU) with that of I-picture data (paragraph 0117) or recording the head position of each I-picture data in a management area (paragraph 0118).
The streamer standard packetizes and records irrespective of contents to be recorded. For this reason, upon playback, the arrival time of packets that store the recorded contents can be detected, but the playback time of the recorded contents cannot be directly detected. Hence, it is not easy for the user to designate the playback start position on a time basis, and playback operations such as time search and the like are inconvenient.
As a disc recorder standard free from the above inconvenience (of time search and the like), the DVD video recording (DVD-VR) standard is known, and many products based on this DVD video recording standard are currently commercially available. This video recording standard adopts time map information. With this time map information (which is not available in the streamer standard), it is easy for the user to designate the playback start position on a time basis.
However, the video recording standard is not compatible to stream recording of digital TV broadcast (in order to record digital broadcast contents using a recorder based on the video recording standard, an analog video signal that has temporarily undergone D/A conversion is sent from the STB to the analog video input of the recorder and is MPEG-encoded in the recorder again, and the encoded data is digitally recorded on a DVD-RAM disc or the like). Therefore, the existing video recording standard cannot meet needs of users who want to air-check digital TV broadcast contents (especially, Hi-Vision programs) while maintaining their quality.